Fire prevention in a network device with redundant power supplies

ABSTRACT

A device may include multiple power supplies that are cooled by a system fan. The power supplies may be cross-connected to supply power to one another and the device may monitor temperatures of the power supplies. Based on the temperatures of the power supplies, the device may determine whether any of the power supplies are likely to be on fire. The device may shut off the fan when a power supply is determined to be likely to be on fire.

BACKGROUND

Network devices, such as routers, security devices (e.g., firewalls),switches, or other network devices, may include multiple power suppliesfor added network device reliability. The power supplies may beredundantly configured so that either of the multiple power supplies mayindependently power the network device. The power supplies may also behot-swappable so that one of the redundant power supplies can bereplaced without disrupting operation of the network device.

Network devices installed in certain locations may be required to passenvironmental design guidelines, such as guidelines stipulated by law orby industry standard. For example, the Network Equipment Building System(NEBS) standard GR-63-CORE is a commonly used set of safety andenvironmental design guidelines for telecommunications equipment. UnderNEBS, during a fire test, the power supply unit under test is set onfire via a gas burn injected into the (horizontal) air flow inlet of oneof the power supplies of the network device for 120 seconds. After theinjected gas burn, the power supply is required to self-extinguish thefire and flames and burning particles should not exit from the networkdevice.

Network devices with redundant power supplies have an increased risk offailing the NEBS fire test, as one of the redundant power supplies maycontinue to run and to power fans of the network device. The runningfans may stimulate the fire in the power supply being tested.

SUMMARY

One implementation may be directed to a device comprising a first powersupply to generate power for the device. The first power supply mayinclude a first temperature sensor to measure a temperature of the firstpower supply and a first communication component to transmit themeasured temperature of the first power supply. The device may furtherinclude a second power supply to generate power for the device, thesecond power supply including: a second temperature sensor to measure atemperature of the second power supply and a second communicationcomponent to transmit the measured temperature of the second powersupply. Power signals from the first power supply and the second powersupply may be cross-connected with one another, in the device, toredundantly power the first temperature sensor, the first communicationcomponent, the second temperature sensor, and the second communicationcomponent. The device may further include at least one fan, locatedwithin the device and external to the first and second power supplies.The device may further include a fan control component to receive themeasured temperatures from the first and second power supplies,determine, based on the measured temperatures from the first and secondpower supplies, when one of the measured temperatures from the first andsecond power supplies include a temperature value indicating that thefirst or second power supply is likely to be experiencing a fire, andshut off operation of the at least one fan in response to thedetermination that the first or second power supply is likely to beexperiencing a fire.

In another implementation, a device may include a first power supplyslot to receive a first removable power supply to generate power for thedevice and a second power supply slot to receive a second removablepower supply to generate power for the device. The device may furtherinclude at least one fan, located within the device and external to thefirst and second power supply slots. The device may further include amidplane to connect components of the device, the midplane including atleast one electrical path to cross-connect logic level power signalsgenerated by the first and second removable power supplies, and at leastone control signal path. The device may further include a fan controlcomponent to receive temperature signals over the control signal path,determine, based on the received temperature signals, whether a fire isoccurring in the device, and shut off operation of the at least one fanwhen a fire is determined to be occurring in the device.

In another implementation, device implemented method may includemonitoring temperature measurements of power supplies in the device, thepower supplies being cross-connected to supply power to one another. Themethod may further include determining, based on the temperaturemeasurements, whether any of the power supplies are likely to be onfire; and shutting off one or more fans of the device in response to thedetermination that at least one of the plurality of the power suppliesare likely to be on fire.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate one or more implementationsdescribed herein and, together with the description, explain theinvention. In the drawings,

FIGS. 1A and 1B are diagrams illustrating perspective views of anexample network device in which implementations described herein may beimplemented;

FIG. 2 is a diagram illustrating an example of an implementation of thenetwork device shown in FIGS. 1A and 1B;

FIG. 3 is a diagram illustrating an example of a device (or a portion ofa device) that may be included in the network device shown in FIGS. 1Aand 1B;

FIG. 4 is a diagram illustrating an example of functional elements ofthe monitor/control component shown in FIG. 2;

FIG. 5 is diagram conceptually illustrating an example of functionalcomponents for preventing the spread of fire in a network device; and

FIG. 6 is a flow chart illustrating an example process for preventingthe spread of fire in a network device.

DETAILED DESCRIPTION

The following detailed description refers to the accompanying drawings.The same reference numbers in different drawings may identify the sameor similar elements.

Techniques described herein may relate to fire prevention andextinguishment in network devices. A network device may include multiplepower supplies that are cooled by a system fan. In one implementation, alogic level power line, such as a power line that can be used to power atemperature sensor, may be cross-routed between the two power suppliesso that a temperature sensor in each power supply may be redundantlypowered from either power supply. When one of the temperature sensorsregisters an abnormally high temperature reading that may indicate afire, the network device may shut off one or more of the system fans tolimit and/or stop the spread of the fire. Because the temperaturesensors, in the power supplies, include a power connection from theother power supply, the temperature sensor may continue to functiondespite a failure (e.g., due to the fire) of the power supply local tothe temperature sensor.

FIGS. 1A and 1B are diagrams illustrating perspective views of anexample network device 100 in which implementations described herein maybe implemented. Network device 100 may include a network device, such asa router, switch, firewall, combined router/firewall, or another type ofnetwork device. In one implementation, network device 100 may include asecure router that supports features such as a firewall and virtualprivate network (VPN) services. In other possible implementations,network device 100 may implement other types of network devices.

FIG. 1A is an example of a front view of network device 100. As shown,network device 100 may include a chassis 110. Chassis 110 may include anumber of ports 120-1 to 120-16 (referred to collectively as “ports 120”or singularly as “port 120”) and expansion slots 130-1 to 130-4(referred to collectively as “expansion slots 130” or singularly as“expansion slot 130”). Each port 120 may include a physical slot intowhich a cable, such as an Ethernet cable, may be inserted. In someimplementations, network device 100 may include connections for othertypes of links, such as optical links. Expansion slots 130 may includeslots into which additional components, such as slide-in cards, may beadded to enhance the functionality of network device 100. Expansionslots 130 may be used to add, for example, additional ports, additionalprocessing capacity, or other components to network device 100.

FIG. 1B is an example of a back view of a portion of network device 100.Network device 100 may include slots 140 and 150 for inserting powersupplies. An example power supply 160, partially inserted into slot 150,is also shown in FIG. 1B.

Slots 140 and 150 may each accept a power supply, such that networkdevice 100 can be configured as a redundant dual power supply system, inwhich each power supply may be capable of supporting the entire load ofnetwork device 100. Accordingly, network device 100 may continue tofunction after the failure or removal of one power supply. In oneimplementation, slots 140 and 150 may be hot swappable so that, as longas at least one power supply 160 remains inserted into network device100, another power supply 160 can be removed/inserted while networkdevice 100 continues to operate.

Power supply 160 may include an alternating current (AC) plug 165, forconnecting to an AC power supply, a handle 170 for removing andinserting of power supply 160 into chassis 110 of network device 100,and cooling vents 175. Internally, power supply 160 may convert theinput AC power to direct current (DC) power and supply the DC power tothe operational components of network device 100. Power supply 160 maybe designed to be a fanless device that is cooled using air flow that ismoved through cooling vents 175 by cooling fans located among theoperational components of network device 100.

FIG. 2 is a diagram illustrating an example of an implementation ofnetwork device 100. As shown, network device 100 may be structured asthree logical units: a power supply section, including multiple powersupplies, labeled as power supplies 210-1 and 210-2; a midplane 220; andan operational system 230.

Power supplies 210-1 and 210-2 may each be hot-swappable power supplies,such as power supplies corresponding to power supply 160. Each powersupply 210 may include an AC/DC conversion component 212 and amonitor/control component 214. AC/DC conversion component 212 mayoperate to convert AC input power to DC output power that may be used byoperational system 230. AC/DC conversion component 212 may output one ormore regulated DC power signals. For example, AC/DC conversion component212 may output a 12V power line and a 3V power line to operationalsystem 230. In one implementation, AC/DC conversion component 212 mayinclude a switched-mode power supply.

Monitor/control component 214 may include logic to monitor and/orcontrol the operation of power supply 210. For example, monitor/controlcomponent 214 may include a temperature sensor to take temperaturereadings of power supply 210 and communication circuitry, such as abuffer, to transmit the temperature readings to operational system 230.

Midplane 220 may include one or more electrical connections in networkdevice 100 that connect various components of network device 100.Midplane 220 may include data distribution paths, control signal paths,and/or power distribution paths. In FIG. 2, power distribution paths 222(12V path) and 224 (3.3V path) are particularly shown. Powerdistribution path 222 may provide a 12V power signal from each one ofpower supplies 210-1 and 210-2 to operational system 230. Powerdistribution path 224 may provide a 3.3V power signal path between powersupplies 210-1 and 210-2. Power distribution path 224 may particularlyprovide power to monitor/control components 214. Because powerdistribution path 224 is sourced from both of power supplies 210-1 and210-2, both monitor/control components 214 may continue to receive powerdespite the failure of one of power supplies 210-1 or 210-2. In additionto power distribution paths, midplane 220 may include other paths, suchas control path 226, which may include a bus through which controlinformation, such as temperature measurements, may be transmitted frommonitor/control components 214 to operational system 230.

In one implementation, control path 226 may be a shared control path,such as an PC (Inter-Integrated Circuit) bus, a 1-wire bus, or othertype of serial communication path or bus.

Operational system 230 may generally include one or more components toperform the substantive processing of network device 100. For example,for a security router, operational system 230 may include logic toperform routing and/or switching functions, firewall functions, and/orVPN functions. As shown in FIG. 2, operational system 230 may includeone or more fans 232, switches 233, a fan control component 234, andnetwork device operational logic 236. Data, such as packet data fromexternal devices, may be received and transmitted by operational system230 through ports 120.

Fans 232 may include one or more fans that are used to cool networkdevice 100. Fans 232 may be used to cool operational system 230. In oneimplementation, power supplies 160/210 may be fanless power suppliesthat may include vents, such as cooling vents 175, that allow airflowfrom fans 232 to also cool power supplies 160/210. Fan control component234 may control fans 232. For instance, fan control component 234 mayadjust the rotational speed and/or selectively turn on/off fans 232 inorder to maintain the correct operational temperatures of network device100. Fan control component 234 may receive temperature signals, such astemperature readings from monitor/control component 214 via control path226. Fan control component 234 may also receive temperature signals fromother components of network device 100, such as from network deviceoperational logic 236. Although shown as a separate component in FIG. 2,in some implementations, fan control component 234 may be implemented aspart of network device operational logic 236, such as part of controlsoftware implemented by network device operational logic 236.

Switches 233 may include transistors, mechanical switches, or otherswitches that may be used to control the rotational speed or on/offstate of fans 232. In one implementation, each fan of fans 232 may beindividually controlled through an associated switch. In an alternativeimplementation, all of fans 232 may be controlled as a group.

Network device operational logic 236 may perform the substantive dataprocessing operations of network device 100. When network device 100 isa router, network device operational logic 236 may include, for example,a hardware component, such as an application specific integrated circuit(ASIC), to quickly and efficiently process and switch packets incomingat one of ports 120 to another outbound port 120, based on headerinformation in the packet. Network device operational logic 236 may alsoinclude one or more general purpose processors to perform otherfunctions, such as functions relating to the implementation of routingor other network protocols, device management, and/or other softwarefunctions.

Although FIGS. 1 and 2 illustrate example components of network device100, in some implementations, network device 100 may include fewercomponents, different components, differently arranged components, oradditional components than those depicted in FIGS. 1 and 2.Additionally, or alternatively, one and/or more components of networkdevice 100 may perform one or more tasks described as being performed byone or more other components of network device 100.

FIG. 3 is a diagram illustrating an example of a device 300 (or aportion of a device) that may be included in network device 100. Device300 may be used to implement, for example, portions of network deviceoperational logic 236 and/or fan control component 234. As shown, device300 may include a bus 310, a processor 320, a memory 330, and acommunication interface 340.

Bus 310 may permit communication among the components of device 300.Processor 320 may include one or more processors and/or microprocessorsthat interpret and execute instructions. Additionally or alternatively,processor 320 may be implemented as or include one or moreapplication-specific integrated circuit (ASICs), field-programmable gatearray (FPGAs), or the like. Memory 330 may include a RAM or another typeof dynamic storage device that stores information and instructions forexecution by processor 320, a ROM or another type of static storagedevice that stores static information and instructions for the processor320, and/or some other type of magnetic or optical recording medium andits corresponding drive for storing information and/or instructions.

Communication interface 340 may include any transceiver-like mechanismthat allows device 300 to communicate with other devices and/or systems.For example, communication interface 340 may include mechanisms forcommunicating with monitor/control components 214.

As will be described in detail below, device 300 may perform certainfunctions in response to processor 320 executing software instructionscontained in a non-transitory computer-readable medium, such as memory330. The software instructions may be read into memory 330 from anothercomputer-readable medium or from another device via communicationinterface 340. The software instructions contained in memory 330 maycause processor 320 to perform processes that will be described later.Alternatively, hardwired circuitry may be used in place of or incombination with software instructions to implement processes consistentwith embodiments described herein. Thus, systems and methods describedherein are not limited to any specific combination of hardware circuitryand software.

Although FIG. 3 illustrates example components of device 300, in someimplementations, device 300 may include fewer components, differentcomponents, differently arranged components, or additional componentsthan those depicted in FIG. 3. Additionally, or alternatively, one ormore components of device 300 may perform one or more tasks described asbeing performed by one or more other components of device 300.

FIG. 4 is a diagram illustrating an example of functional elements ofmonitor/control component 214. Monitor/control component 214 may includea temperature sensor 410 and a communication component 420. Temperaturesensor 410 and communication component 420 may be powered by a redundantpower supply, such as power distribution path 224 (e.g., a 3.3V powerline that is supplied by power supplies 210-1 and/or 210-2).

Temperature sensor 410 may take temperature readings of its power supply210. Temperature sensor 410 may include, for example, a thermistor oranother type of temperature sensor. In one implementation, temperaturesensor 410 may be a sensor that is designed to operate over a relativelylarge range, such as a range including temperature values that may bemuch higher than would be expected during normal operation of powersupply 210, such as up to temperatures that may occur during a fire inpower supply 210 (e.g., a temperature value during normal operation maybe 50 degrees C. and a temperature value during a fire may be 500degrees C.).

Communication component 420 may include logic to transmit information,such as temperature measurements from temperature sensor 410, tooperational system 230 (i.e., over midplane 220). Communicationcomponent 420 may include, for example, a buffer to store and source themeasured temperature values over control path 226 to fan controlcomponent 234. Alternatively or additionally, communication component420 may include logic (e.g., an integrated circuit) to implement acommunication protocol over control path 226. Communication component420 may alternatively or additionally include other elements, such as anElectrically Erasable Programmable Read-Only Memory (EEPROM) that maystore an identifier of the power supply. In this implementation, eachpower supply 210 may include a different identifier and each temperaturereading may be transmitted to fan control component 234 with itscorresponding power supply identifier. In this manner, fan controlcomponent 234 may receive, over a shared control communication path,temperature readings (and potentially other state/monitor information),from power supplies 210. As will be described in more detail below, fancontrol component 234 may control fans 232 based on the temperatures ofpower supplies 210.

In one implementation, temperature sensor 410 and communicationcomponent 420 may be placed in power supply 210 in a way that makes afire occurrence in power supply 210 unlikely to disrupt the operationtemperature sensor 410 and communication component 420. For example,temperature sensor 410 and communication component 420 may be physicallyseparated from AC/DC conversion component 212 or “hardened” in some way(e.g., by enclosing temperature sensor 410 and communication component420 in an air-tight container) to make temperature sensor 410 andcommunication component 420 resistant to fire.

Although FIG. 4 illustrates example functional elements ofmonitor/control component 214, in some implementations, monitor/controlcomponent 214 may include fewer components, different components,differently arranged components, and/or additional components than thosedepicted in FIG. 4. Additionally, or alternatively, one or morecomponents shown in FIG. 4 may perform one or more tasks described asbeing performed by one or more other components.

FIG. 5 is diagram conceptually illustrating an example of functionalcomponents 500 for preventing the spread of fire in a network device.Functional components 500 may be implemented by, for example, acombination of temperature sensor 410, communication component 420, andfan control component 234. Functional components 500 may includetemperature 510, temperature 520, temperature monitor 530, switches 233,and fans 232.

Functional components 500 may receive multiple temperature measurementvalues, labeled as temperature 510 (temperature 1) and temperature 520(temperature 2). As previously discussed, the temperature values maycorrespond to temperature readings from within power supplies 210-1 and210-2. The temperature of each power supply 210 may be measured bytemperature sensors 410, transmitted over midplane 220 (e.g., viacontrol path 226), and received by temperature monitor 530.

Temperature monitor 530 may monitor temperature 510 and temperature 520.Temperature monitor 530 may determine when one of temperatures 510 or520 increases to a value above a first threshold. The threshold may beselected as a temperature that is above the normal operation of one ofpower supplies 210, such as a temperature value that is consistent witha fire in the power supply. In one implementation, temperature monitor530 may determine when one of temperatures 510 or 520 is above the firstthreshold while the other one of temperatures 510 or 520 remain within anormal range. Alternatively, temperature monitor 530 may determinewhether either one of temperatures 510 or 520 is above the firstthreshold (without regard to the other temperature 510 or 520). Whenthis condition is satisfied, temperature monitor 530 may output an“extreme temperature signal.” In one implementation, the extremetemperature signal, when activated, may control switches 233 to cut-offpower supplied to fans 232. Stopping the operation of fans 232 mayreduce airflow through network device 100, and thus decrease thepotential for the fire to spread outside of network device 100 and/orhelp to extinguish the fire. In some implementations, various fans 232may control airflow in various portions of network device 100. Forexample, a first fan may provide airflow to power supply 210-1 and asecond fan may provide airflow to power supply 210-2. In this situation,temperature monitor 530 may only stop the operation of the fan thatprovides airflow to the power supply in which an extreme temperature isdetected.

In one implementation, temperature monitor 530, in addition tocontrolling fans 232, may perform other actions in response to thedetection of an extreme temperature. For example, in response todetection of an extreme temperature, temperature monitor 530 may turnoff other elements in power supplies 210 and may transmit an alert to anadministrator or may perform other functions.

Although FIG. 5 illustrates example functional elements 500, in someimplementations, monitor/control component 214 may include fewercomponents, different components, differently arranged components, oradditional components than those depicted in FIG. 5. Additionally, oralternatively, one or more components shown in FIG. 5 may perform one ormore tasks described as being performed by one or more other components.

FIG. 6 is a flow chart illustrating an example process 600 forpreventing the spread of fire in a network device.

Process 600 may include providing cross-connected power from powersupplies 210 (block 610). The cross-connected power from power supplies210 may be designed to supply backup logic level operational power totemperature sensors (and communication logic needed to communicatetemperature readings) in power supplies 210 (block 610). For example, asshown in FIG. 2, network device 100 may include a power signal path 224that is routed through midplane 220 and that connects to the outputpower of each power supply 210 and to monitor/control component 214 ofeach power supply 210.

Process 600 may also include monitoring the temperatures of powersupplies 210 (block 620). As previously discussed, monitor/controlcomponents 214 may include temperature temperature sensors 410 that maytransmit, via control path 226, temperature readings to operationalsystem 230. Fan control component 234 in operational system 230 maycompare the read temperature values to threshold values. The thresholdvalues may be, for example, set during design or manufacture of networkdevice 100.

Process 600 may further include determining when an extreme temperatureis detected (block 630). For example, an extreme temperature may bedetected when a measured temperature is greater than the thresholdvalue. Detection of an extreme temperature may indicate that a fire isoccurring in one of power supplies 210 of network device 100. Inresponse to detection of an extreme temperature (block 630—YES), process600 may further include shutting down the fans of network device 100(block 640). As previously discussed, switches 233 may be used to turnoff one or more of fans 232 in network device 100. When an extremetemperature is not detected, (block 630—NO), process 600 may continue tomonitor the temperatures of power supplies 210 (block 620).

In some implementations, after the fans are shutdown (block 640), thetemperature of power supplies 210 may continue to be monitored. If thetemperature reduces to a normal level, the fans may be restarted.

As described above, fires in a power supply of a network device may bedetected even when the power supply that is on fire has failed. Fans inthe network device may be stopped to assist in the extinguishment of thefire.

It will also be apparent that aspects described herein may beimplemented in many different forms of software, firmware, and hardwarein the implementations illustrated in the figures. The actual softwarecode or specialized control hardware used to implement aspects describedherein is not intended to limit the scope of the invention. Thus, theoperation and behavior of the aspects were described without referenceto the specific software code—it being understood that software andcontrol hardware can be designed to implement the aspects based on thedescription herein.

While series of blocks have been described in FIG. 6, the order of theblocks may vary in other implementations. Also, non-dependent blocks maybe performed in parallel.

Even though particular combinations of features are recited in theclaims and/or disclosed in the specification, these combinations are notintended to limit the invention. In fact, many of these features may becombined in ways not specifically recited in the claims and/or disclosedin the specification. Although each dependent claim listed below maydirectly depend on only one other claim, the disclosure of the inventionincludes each dependent claim in combination with every other claim inthe claim set.

Further, certain aspects described herein may be implemented as “logic”or as a “component” that performs one or more functions. This logic orcomponent may include hardware, such as an ASIC or a FPGA, or acombination of hardware and software.

No element, act, or instruction used in the description of the presentapplication should be construed as critical or essential to theinvention unless explicitly described as such. Also, as used herein, thearticle “a” is intended to include one or more items. Where only oneitem is intended, the term “one” or similar language is used. Further,the phrase “based on” is intended to mean “based, at least in part, on”unless explicitly stated otherwise. The scope of the invention isdefined by the claims and their equivalents.

What is claimed is:
 1. A device comprising: a first power supply slot toreceive a first removable power supply to generate power for the device;a second power supply slot to receive a second removable power supply togenerate power for the device; at least one fan, located within thedevice and external to the first and second power supply slots; amidplane to connect components of the device, the midplane including: atleast one electrical path to cross-connect logic level power signalsgenerated by the first and second removable power supplies, and at leastone control signal path; and a fan control component to: receivetemperature signals over the at least one control signal path,determine, based on the received temperature signals, whether a fire isoccurring in the device, and shut off operation of the at least one fanwhen the fire is determined to be occurring in the device.
 2. The deviceof claim 1, further comprising: network device operational logic toperform network operations.
 3. The device of claim 2, furthercomprising: a plurality of ports through which the network deviceoperational logic receives and transmits packets.
 4. The device of claim1, where the at least one fan includes: a plurality of fans locatedwithin the device and external to the first and second power supplyslots, and where the fan control component shuts off operation of selectones of the plurality of fans based on a determination that the fire isoccurring in the device.
 5. The device of claim 1, where thedetermination of whether the fire is occurring in the device is based ona comparison of the received temperature signals to a thresholdtemperature value.
 6. The device of claim 1, where the device includes arouter, a switch, or a firewall.
 7. The device of claim 1, where the atleast one control signal path includes a serial communication bus.
 8. Amethod comprising: receiving, by a first power supply slot of a device,a first removable power supply to generate power for the device;receiving, by a second power supply slot of the device, a secondremovable power supply to generate power for the device, at least onefan being located within the device and being external to the firstpower supply slot and the second power supply slot; receiving, by a fancontrol component of the device, temperature signals over at least onecontrol signal path included in a midplane of the device, the midplaneto connect components of the device, the midplane further including atleast one electrical path to cross-connect logic level power signalsgenerated by the first removable power supply and the second removablepower supply; determining, by the fan control component of the deviceand based on the received temperature signals, whether a fire isoccurring in the device; and shutting off, by the fan control componentof the device, the at least one fan when the fire is occurring in thedevice.
 9. The method of claim 8, where determining whether the fire isoccurring includes comparing the temperature signals to a thresholdtemperature value.
 10. The method of claim 8, further comprising:performing network operations using network device operational logic ofthe device.
 11. The method of claim 8, further comprising: receiving andtransmitting packets via a plurality of ports of the device.
 12. Themethod of claim 8, where the at least one fan includes: a plurality offans located within the device and external to the first power supplyslot and the second power supply slot, and where shutting off the atleast one fan includes: selectively shutting off ones of the pluralityof fans when the fire is occurring in the device.